[PATCH v12 Kernel 7/7] vfio: Selective dirty page tracking if IOMMU backed device pins pages

[Kirti Wankhede <kwankhede@nvidia.com>]

Added a check such that only singleton IOMMU groups can pin pages.
From the point when vendor driver pins any pages, consider IOMMU group
dirty page scope to be limited to pinned pages.

To optimize to avoid walking list often, added flag
pinned_page_dirty_scope to indicate if all of the vfio_groups for each
vfio_domain in the domain_list dirty page scope is limited to pinned
pages. This flag is updated on first pinned pages request for that IOMMU
group and on attaching/detaching group.

Signed-off-by: Kirti Wankhede <kwankhede@nvidia.com>
Reviewed-by: Neo Jia <cjia@nvidia.com>
---
 drivers/vfio/vfio.c             | 13 +++++++-
 drivers/vfio/vfio_iommu_type1.c | 72 +++++++++++++++++++++++++++++++++++++++--
 include/linux/vfio.h            |  4 ++-
 3 files changed, 84 insertions(+), 5 deletions(-)

diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index c8482624ca34..a941c860b440 100644
--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -87,6 +87,7 @@ struct vfio_group {
 	bool				noiommu;
 	struct kvm			*kvm;
 	struct blocking_notifier_head	notifier;
+	bool				is_singleton;
 };
 
 struct vfio_device {
@@ -838,6 +839,12 @@ int vfio_add_group_dev(struct device *dev,
 		return PTR_ERR(device);
 	}
 
+	mutex_lock(&group->device_lock);
+	group->is_singleton = false;
+	if (list_is_singular(&group->device_list))
+		group->is_singleton = true;
+	mutex_unlock(&group->device_lock);
+
 	/*
 	 * Drop all but the vfio_device reference.  The vfio_device holds
 	 * a reference to the vfio_group, which holds a reference to the
@@ -1895,6 +1902,9 @@ int vfio_pin_pages(struct device *dev, unsigned long *user_pfn, int npage,
 	if (!group)
 		return -ENODEV;
 
+	if (!group->is_singleton)
+		return -EINVAL;
+
 	ret = vfio_group_add_container_user(group);
 	if (ret)
 		goto err_pin_pages;
@@ -1902,7 +1912,8 @@ int vfio_pin_pages(struct device *dev, unsigned long *user_pfn, int npage,
 	container = group->container;
 	driver = container->iommu_driver;
 	if (likely(driver && driver->ops->pin_pages))
-		ret = driver->ops->pin_pages(container->iommu_data, user_pfn,
+		ret = driver->ops->pin_pages(container->iommu_data,
+					     group->iommu_group, user_pfn,
 					     npage, prot, phys_pfn);
 	else
 		ret = -ENOTTY;
diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index f748a3dbe9f9..a787a2bcd757 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -71,6 +71,7 @@ struct vfio_iommu {
 	bool			v2;
 	bool			nesting;
 	bool			dirty_page_tracking;
+	bool			pinned_page_dirty_scope;
 };
 
 struct vfio_domain {
@@ -98,6 +99,7 @@ struct vfio_group {
 	struct iommu_group	*iommu_group;
 	struct list_head	next;
 	bool			mdev_group;	/* An mdev group */
+	bool			has_pinned_pages;
 };
 
 struct vfio_iova {
@@ -129,6 +131,10 @@ struct vfio_regions {
 static int put_pfn(unsigned long pfn, int prot);
 static unsigned long vfio_pgsize_bitmap(struct vfio_iommu *iommu);
 
+static struct vfio_group *vfio_iommu_find_iommu_group(struct vfio_iommu *iommu,
+					       struct iommu_group *iommu_group);
+
+static void update_pinned_page_dirty_scope(struct vfio_iommu *iommu);
 /*
  * This code handles mapping and unmapping of user data buffers
  * into DMA'ble space using the IOMMU
@@ -580,11 +586,13 @@ static int vfio_unpin_page_external(struct vfio_iommu *iommu,
 }
 
 static int vfio_iommu_type1_pin_pages(void *iommu_data,
+				      struct iommu_group *iommu_group,
 				      unsigned long *user_pfn,
 				      int npage, int prot,
 				      unsigned long *phys_pfn)
 {
 	struct vfio_iommu *iommu = iommu_data;
+	struct vfio_group *group;
 	int i, j, ret;
 	unsigned long remote_vaddr;
 	struct vfio_dma *dma;
@@ -661,8 +669,14 @@ static int vfio_iommu_type1_pin_pages(void *iommu_data,
 			}
 		}
 	}
-
 	ret = i;
+
+	group = vfio_iommu_find_iommu_group(iommu, iommu_group);
+	if (!group->has_pinned_pages) {
+		group->has_pinned_pages = true;
+		update_pinned_page_dirty_scope(iommu);
+	}
+
 	goto pin_done;
 
 pin_unwind:
@@ -938,8 +952,11 @@ static int vfio_iova_dirty_bitmap(struct vfio_iommu *iommu, dma_addr_t iova,
 		unsigned int npages = 0, shift = 0;
 		unsigned char temp = 0;
 
-		/* mark all pages dirty if all pages are pinned and mapped. */
-		if (dma->iommu_mapped) {
+		/*
+		 * mark all pages dirty if any IOMMU capable device is not able
+		 * to report dirty pages and all pages are pinned and mapped.
+		 */
+		if (!iommu->pinned_page_dirty_scope && dma->iommu_mapped) {
 			iova_limit = min(dma->iova + dma->size, iova + size);
 			npages = iova_limit/pgsize;
 			bitmap_set(dma->bitmap, 0, npages);
@@ -1479,6 +1496,51 @@ static struct vfio_group *find_iommu_group(struct vfio_domain *domain,
 	return NULL;
 }
 
+static struct vfio_group *vfio_iommu_find_iommu_group(struct vfio_iommu *iommu,
+					       struct iommu_group *iommu_group)
+{
+	struct vfio_domain *domain;
+	struct vfio_group *group = NULL;
+
+	list_for_each_entry(domain, &iommu->domain_list, next) {
+		group = find_iommu_group(domain, iommu_group);
+		if (group)
+			return group;
+	}
+
+	if (iommu->external_domain)
+		group = find_iommu_group(iommu->external_domain, iommu_group);
+
+	return group;
+}
+
+static void update_pinned_page_dirty_scope(struct vfio_iommu *iommu)
+{
+	struct vfio_domain *domain;
+	struct vfio_group *group;
+
+	list_for_each_entry(domain, &iommu->domain_list, next) {
+		list_for_each_entry(group, &domain->group_list, next) {
+			if (!group->has_pinned_pages) {
+				iommu->pinned_page_dirty_scope = false;
+				return;
+			}
+		}
+	}
+
+	if (iommu->external_domain) {
+		domain = iommu->external_domain;
+		list_for_each_entry(group, &domain->group_list, next) {
+			if (!group->has_pinned_pages) {
+				iommu->pinned_page_dirty_scope = false;
+				return;
+			}
+		}
+	}
+
+	iommu->pinned_page_dirty_scope = true;
+}
+
 static bool vfio_iommu_has_sw_msi(struct list_head *group_resv_regions,
 				  phys_addr_t *base)
 {
@@ -1885,6 +1947,7 @@ static int vfio_iommu_type1_attach_group(void *iommu_data,
 
 			list_add(&group->next,
 				 &iommu->external_domain->group_list);
+			update_pinned_page_dirty_scope(iommu);
 			mutex_unlock(&iommu->lock);
 
 			return 0;
@@ -2007,6 +2070,7 @@ static int vfio_iommu_type1_attach_group(void *iommu_data,
 done:
 	/* Delete the old one and insert new iova list */
 	vfio_iommu_iova_insert_copy(iommu, &iova_copy);
+	update_pinned_page_dirty_scope(iommu);
 	mutex_unlock(&iommu->lock);
 	vfio_iommu_resv_free(&group_resv_regions);
 
@@ -2021,6 +2085,7 @@ static int vfio_iommu_type1_attach_group(void *iommu_data,
 out_free:
 	kfree(domain);
 	kfree(group);
+	update_pinned_page_dirty_scope(iommu);
 	mutex_unlock(&iommu->lock);
 	return ret;
 }
@@ -2225,6 +2290,7 @@ static void vfio_iommu_type1_detach_group(void *iommu_data,
 		vfio_iommu_iova_free(&iova_copy);
 
 detach_group_done:
+	update_pinned_page_dirty_scope(iommu);
 	mutex_unlock(&iommu->lock);
 }
 
diff --git a/include/linux/vfio.h b/include/linux/vfio.h
index e42a711a2800..da29802d6276 100644
--- a/include/linux/vfio.h
+++ b/include/linux/vfio.h
@@ -72,7 +72,9 @@ struct vfio_iommu_driver_ops {
 					struct iommu_group *group);
 	void		(*detach_group)(void *iommu_data,
 					struct iommu_group *group);
-	int		(*pin_pages)(void *iommu_data, unsigned long *user_pfn,
+	int		(*pin_pages)(void *iommu_data,
+				     struct iommu_group *group,
+				     unsigned long *user_pfn,
 				     int npage, int prot,
 				     unsigned long *phys_pfn);
 	int		(*unpin_pages)(void *iommu_data,
-- 
2.7.0